Sample carriers of the above type comprise a receiving part with deepened portions formed therein. The samples provided for examination will be introduced into the deepened portions. Part of the deepened portions are formed to extend wholly through the receiving part; therefore, these deepened portions are closed by a base part. The base part is provided e.g. as a glass plate or a transparent film. Normally, the base part is permeable to light of specific wavelengths so that the samples accommodated in the continuous deepened portions can be examined using a microscope or the like. Especially for the application of screening methods, the base part is permeable to visible light. In examination methods such as the screening method, use is made also of sample carriers wherein the base parts are not transparent to visible light. Such sample carriers will then comprise base parts is which are permeable to specific wavelength ranges in which e.g. a fluorescence of sample components will occur.
The sample carriers can be e.g. titration plates having their individual deepened portions arranged at uniform distances from each other. Particularly, the samples received in the deepened portions are minimum-sized samples of a volume smaller than 1 ml. Further, titration plates are already known which are suited for the examination of sample quantities in the microliter or even sub-microliter range.
Further, the sample carriers can be provided as chips. In chip-like sample carriers, the deepened portions are normally formed as one or a plurality of channels, and the chips contain one or a plurality of liquid reservoirs. For instance, the chips can be microfluidic chips comprising preferably two reservoirs connected to each other via a channel. Between the two reservoirs, a fluid exchange will occur which can be controlled by suitable valves, membranes and/or ion barriers. Such chips are useful, for instance, for controlling the mixing behavior of liquids, e.g. under the influence of electromagnetic forces. To allow for the examination of the behavior of the liquids, the bottom of a liquid reservoir and/or of a chip channel is preferably transparent. For this purpose, in turn, a base part is provided in order to close the deepened portions such as e.g. the reservoirs or the channel. The base part preferably is a glass plate or a transparent film.
Attachment of the base parts to the receiving part comprising the deepened portions is performed e.g. by bonding. For this purpose, the receiving part 10 (FIG. 3) is provided with a rectangular deepened portion 12 into which a glass plate 14 is inserted. The glass plate 14 will thus be centered in the rectangular deepened portion 12. The bonding agent is applied e.g. by tampon pressure onto the inner side 16 of base part 14 and onto the bottom side 18 of receiving part 10 comprising the deepened portions 20. Since the base part 14 must close the deepened portions 20 tightly, the base part 14 is firmly pressed onto the bottom side 18 of receiving part 10. Further, it has to be safeguarded that bonding agent is applied between all of the webs of the deepened portions 20 serving as connection points. In such known sample carriers, bonding agent 22 will be squeezed out along the outer edge of base part 14. This excess bonding agent 22 reaches a lower edge 24 of base part 14.
In the above process, it may happen that bonding agent 22 flows so far into the interior region that outer deepened portions 20 will be at least partially covered by the bonding agent 22. This has the consequence that an optical examination of the samples located in these deepened portions 20 is adulterated because the light signal is e.g. refracted by the bonding agent. Thus, after the base part 14 has been attached by bonding, it is required to clean the base part in the edge region. Cleaning is performed e.g. by a piece of cloth soaked with alcohol or the like. In this case, residues remain on the outer side 24 of base part 14. These will cause adulterations of the measurement results. As a result, the outer deepened portions are often unfit for use.
It is an object of the invention to provide a sample carrier for receiving chemical and/or biological samples wherein a contamination of the base part which would impair the examination of the samples is avoided.